Hitchhiker's Guide To The Galaxy, The - Speaking of Missing Translators

OK, the very first scene where the Earth is about to be destroyed and Pro. Vogon Gents is telling the Earth creatures that the plans had been at Alpha Centuri... that whole sequence! Think about it. How could the Earth creatures understand what P.V.G. was saying without every single person having a babel fish? We know that the people understood what he was saying as P.V.G. kept answering the people. I mean I guess there could have been a loud speaker translator, however, wouldn't it have been activated when Ford and Arthur hitched a ride?

First of all, the reason the people of earth understood him WAS because of a translator. Secondly, the reason they didn't use it on "the hitchhikers" is because they were just that to the Vogon fleet. No planetary background is known about either of them. And it seems impractical and would require alot of time for Adams to have them go through every planetary language for "the hitchhikers" to understand. Especially given the fate which the vogons have in store for them.